Two kinds of representative machine-made aggregates,namely the calcium-base and silialuminate-base,were chosen in the experimental study.Through analysis of SEM,it was found that the former's main chemical component was calcium carbonate with an island like structure,the latter might be a rock of silialuminate-base in a state of sandwich.Through experiments of the paste fluidity,Zeta potential and concrete test with different water-reducers it is shown that the calcium-base aggregate,which could be easily used to prepare high workability and high strength concrete with polycarboxylate water-reducer,has lower water absorption ability and good adaptability with any water-reducer,whereas the silialuminate-base aggregate has higher water absorption ability,higher zeta potential value and poor adaptability so that there might be a problem to produce HPC by using high performance polycarboxylate water-reducer.